The present invention relates to an apparatus and method that dehumidifies and cools air. More specifically, the present invention discloses an apparatus that preconditions air by utilizing the thermal swing created when hydrogen gas is transferred between hydrogen storage materials to cool and dehumidify incoming or internally re-circulated air and reduce energy costs.
Hydrogen is the xe2x80x9cultimate fuelxe2x80x9d for the next millennium, and, it is inexhaustible. Hydrogen is the most plentiful element in the universe and can provide an inexhaustible, clean source of energy for our planet, which can be produced by various processes, which include the splitting of water into hydrogen and oxygen. The hydrogen can be stored and transported in solid-state form.
In the past considerable attention has been given to the use of hydrogen as a fuel or fuel supplement. While the world""s oil reserves are depletable, the supply of hydrogen remains virtually unlimited. Hydrogen can be produced from coal, natural gas and other hydrocarbons, or formed by the electrolysis of water, preferably via energy from the sun which is composed mainly of hydrogen and can, itself, be thought of as a giant hydrogen xe2x80x9cfurnacexe2x80x9d. Moreover hydrogen can be produced without the use of fossil fuels, such as by the electrolysis of water using nuclear or solar energy, or any other form of economical energy (e.g., wind, waves, geothermal, etc.). Furthermore, hydrogen is an inherently low cost fuel. Hydrogen has the highest density of energy per unit weight of any chemical fuel and is essentially non-polluting since the main by-product of xe2x80x9cburningxe2x80x9d hydrogen is water. Thus, hydrogen can be a means of solving many of the world""s energy related problems, such as climate change, pollution, strategic dependency on oil, etc., as well as providing a means of helping developing nations to achieve sustainable growth. However, hydrogen storage principles have not been applied to a preconditioner unit that dehumidifies and cools air and reduces energy consumption.
In the past two decades, heating, ventilation, and air conditioning (HVAC) systems for residential, commercial, and industrial buildings have experienced massive changes. These advanced HVAC systems are currently marketed and used in newly constructed buildings and homes, saving customers billions of dollars. However, there are still tens of millions of existing residential buildings equipped with original, much less energy efficient (up to 30%), HVAC systems. The wasted energy cost that could be recovered from these existing systems through incorporation of energy efficient aftermarket retro-fit kits is estimated at xcx9c$15 billion. Significant reductions of carbon dioxide (CO2) and other pollutants, like nitrous and sulfur oxides (NOx and SO2), would also be realized through the development and mass adoption of Integrated Systems for Energy-Efficient Space Conditioning. Space air conditioning is a vital component of residential HVAC systems and should be targeted to achieve the greatest incremental energy savings.
A study demonstrated that the energy efficiency could be 20 to 30% higher for air conditioning systems that use active desiccant dehumidification in large HVAC systems for commercial or industrial buildings. It was also shown, however, that these systems are most suitable for large buildings and niche markets, where humidity control and outdoor fresh air inflow are very important, such as: hospitals, nursing homes and assisted living quarters, hotels and research facilities. Hospitals and other special RandD facilities need to introduce large amount of fresh air into the buildings, even as the outdoor air temperature is higher than that of the indoor; the HVAC system with the active desiccant demonstrates significant improvement in efficiency. However, this technology is not cost effective for residential markets due to the high capital cost of the desiccant equipment and less energy saving for smaller scale of air-cooling. Therefore, it is perceived by consumers that the energy saving by the active desiccant HVAC system will not offset the upfront cost of the installation.
The majority of residential air conditioning systems are not equipped with separate dehumidification and ventilation systems. The very common case is that homeowners operate a stand-alone dehumidifier in the basement or individual rooms. This type of independent compressor based dehumidifier reduces the humidity of indoor air, but rejects heat into the dried air. The heat that needs to be removed includes the latent enthalpy of condensed water and compressor friction. Existing dehumidifiers reduce the amount of water, but since the heat from the dehumidifier raises the indoor air temperature, more electrical energy needs to be used for the air conditioner to pump the heat out. Therefore, this practice is a very inefficient way to achieve comfort.
As a result of the forgoing, there exists a need in the art for an energy efficient apparatus and method to reduce the energy load on existing AC systems and operate independent of AC systems. To date, no one has applied the hydrogen absorption/desorption capabilities of metal hydrides to dehumidify and cools air. The present invention discloses an energy efficient metal hydride based apparatus and method for reducing the relative humidity of air that may be used to precondition air entering an AC system and utilizing waste heat from the AC system. Additionally, the present invention discloses an energy efficient metal hydride based apparatus and method for reducing the relative humidity of air that may be used independent of an AC system.
The present invention discloses a novel apparatus that provides separate dehumidification and ventilation that may be used to increase the energy efficiency of residential air conditioning systems, in addition to improving indoor air quality and dwelling comfort. The apparatus and method dehumidifies and cools the incoming air by utilizing the thermal swing created when hydrogen is shuttled between metal hydride alloys to cool and dehumidify incoming or internally re-circulated air. The release of hydrogen from a metal hydride matrix is an endothermic process. The dehydriding process absorbs the heat from the surroundings, such as entering or recirculating air. If the thermal energy latent in the incoming air can be used for the dehydriding process, the incoming air temperature will drop. This drop in the temperature can be used to reduce the water content and thus xe2x80x9cpre-conditionxe2x80x9d the incoming air. This pre-conditioned air requires less energy to cool (xe2x80x9cair conditionxe2x80x9d) and because the rate of hydrogen desorption can be regulated, it is possible to actively control humidity levels. This controlled process is powered, preferably by the waste heat of the HVAC system and, thus, significantly improves the efficiency of the overall system. However, the present invention may operate independent of an air conditioning unit. In that embodiment, heat is provided to the system by a different means, such as a solar powered heater.
The metal hydride based air preconditioner of the present invention is fundamentally different from a conventional compressor dehumidifier, and active desiccant based systems. The metal hydride based air preconditioner of the present invention operates by recovering the waste heat from the condenser of the air conditioner. The metal hydride based air preconditioner of the present invention has less moving components and much more energy saving. Since this system is a totally sealed system with no external supply of hydrogen, it is totally safe and reliable. The energy saving is substantial. Not only does it recovers waste heat for the cooling of house air, but it also realizes pre-dehumidification of humid air, which enhances the cooling efficiency of the existing air conditioning system. The installation of an outside air economizer to an existing enclosed area, such as a residential building, improves the indoor air quality and increases comfort; at same time, it is energy saving, environmentally friendly, and potentially cost effective when mass-produced.
The present invention discloses an apparatus and method for cooling and dehumidifying air comprising a first hydrogen storage module having a first plateau pressure at ambient temperature and a second hydrogen storage module having a second plateau pressure at ambient temperature. The present invention may be used in combination with an air conditioning unit or independent of an air conditioning unit. Each hydrogen storage module contains hydrogen storage material(s) that is capable of absorbing and desorbing hydrogen gas. Generally, when hydrogen gas is desorbed from the hydrogen storage material, the hydrogen gas will flow from a higher pressure to a lower pressure. A valve provides flow communication between the first hydrogen storage module and the second hydrogen storage module. At least one reversible first module fan may be positioned to force air to and from the first hydrogen storage module and at least one reversible second module fan may be positioned to force air to and from the second hydrogen storage module. The second module fan may be incorporated to cool the second module or heat the module by forcing waste from the condenser into contact with the second hydrogen storage module. This may further include a control unit operably coupled to the first hydrogen storage module, the second hydrogen storage module, the first module fan, the second module fan and the valve. Preferably, the second pressure is the ambient pressure of the environment at ambient temperature and the first pressure comprises at most 300 psia at the ambient temperature. However, the first plateau pressure may be higher than 300 psia depending on the environmental conditions, such as temperature and altitude. As the second hydrogen storage module is heated, hydrogen gas is released from the hydrogen storage material contained therein and the pressure in the second module rises as the temperature rises. As a result, the pressure of hydrogen gas in the second hydrogen storage module is raised to a point higher than the pressure in the first hydrogen storage module. When the valve is opened, hydrogen gas flows from the second hydrogen storage module into the first hydrogen storage module and the hydrogen gas is absorbed into the hydrogen storage material contained therein and then the valve is closed. Then, the second hydrogen storage module is cooled, preferably by an electric fan powered by solar energy, and the first hydrogen storage module is heated. As a result, the pressure of the hydrogen gas in the first hydrogen storage module is raised to a point higher than the pressure in the second hydrogen storage module. The valve is opened and the hydrogen gas flows back into the second hydrogen storage module. As the hydrogen gas flows to the second hydrogen storage module and the first hydrogen storage module cools, passing air is dehumidified and moisture in the air collects on thermally conductive fins protruding from the first hydrogen storage module. The moisture may be collected and released from the system using a water drain.
The apparatus may further comprise series of conduits to maximize the flow of cool air into and warm air out of to be cooled, such as a residential home. The conduits include a first air conduit having a first end terminating in the area to be cooled and a second end terminating in an area outside the area to be cooled and a second air conduit having a first end terminating in an area to be cooled and a second end terminating in the first air conduit. The first hydrogen storage module may be set in the first air conduit between the first end of the first air conduit and the second end of the second air conduit. The conduits may further comprise a third air having a first end connected to the second end of the first air conduit and a second terminating in the area outside the area to be cooled and a fourth air conduit having a first end terminating in the first air conduit and a second end terminating in the area outside the area to be cooled. Further, an air filter may be set in the third conduit to filter larger particles from the incoming air.
The apparatus may further comprise a means for restricting air flow, such as a damper, in the first air conduit and a means for restricting air flow, such as a damper, in the second air conduit. The first damper may be set to shift from restricting air flow through the first end of the first air conduit and restricting air flow through the first end of the fourth air conduit and the second damper may be adapted to shift from restricting air flow through the second end of said second air conduit and restricting air flow through the second end of the first air conduit. Motors controlling the dampers may be operably coupled to the control unit.
The apparatus may further include a condenser coil that guides a flow of refrigerant pumped by a refrigerant pump through the system to and from the cooling coil of an air conditioner. In an embodiment of the present invention, the condenser coil guides the refrigerant through the condenser only and a fan is used to cool the second hydrogen storage module. In a preferred embodiment, the condenser coil is adapted to guide the refrigerant through the condenser coil and the second hydrogen storage module. In this embodiment, the condenser and the second hydrogen storage module may be compartmentally separated. As the second hydrogen storage module is heated, a series of refrigerant valves guide the refrigerant through the condenser. However, when the second hydrogen storage module is cooled, the refrigerant valves are manipulated to guide the flow of refrigerant through the second hydrogen storage module to assist the fan in cooling. The control unit may control the refrigerant valves.
The present invention discloses a novel method of cooling and dehumidifying air comprising providing a first hydrogen storage module having a first pressure in flow communication with a second hydrogen storage module having a second pressure. The first pressure is higher than the second pressure at ambient temperature. However, the first and second pressures are sufficiently close to enable an increase in temperature of the second hydrogen storage module (to about 120xc2x0 C.) to increase the pressure of the second hydrogen storage module to a level above the ambient temperature pressure of the first hydrogen storage module that forces hydrogen gas from the second hydrogen storage module to flow into the first hydrogen storage module. Further, the method includes a first closing of a valve between the hydrogen storage modules, then heating the second hydrogen storage module, which increases in the second pressure. A first opening of the valve causes hydrogen gas to flow from the second hydrogen storage module into the first hydrogen storage module and an increase in temperature of the first hydrogen storage module, then, preferably after the first hydrogen storage module is fully charged with the hydrogen gas, a second closing of the valve is performed. The second hydrogen storage module is then cooled and the second hydrogen storage module undergoes a reduction in the second pressure. Preferably, the second hydrogen storage module is cooled by a reversible fan. A second opening of the valve causes hydrogen gas to flow from the first hydrogen storage module into the second hydrogen storage module. The desorption of hydrogen gas from the first hydrogen storage module cools the first hydrogen storage module and air flowing past the first hydrogen storage module is dehumidified and cooled.
The method may further comprise a series of conduits to force air flow through various points of the apparatus at the appropriate time. For example, the method may simultaneously include forcing warm air from an area to be cooled in through an air conduit from an outside area, during the desorption of the hydrogen gas from the cooling module, diverting the warm air from the air conduit to an outside area into an air conduit having the cooling module and forcing the dehumidified and cooled air into the area to be cooled through the air conduit having the cooling module. The method may further include simultaneously restricting air flow to the area to be cooled during the heating of the heat retriever module, restricting air flow from the outdoor air conduit and diverting air outside through a different air conduit.